The proposed research examines developmental change in abstraction capabilities underlying sategorization in infants. One of the most important tasks confronting the child over the first years of life is categorization. Through the formation and use of categories, novel experiences become familiar, recognizable and predictable for the child. The investigation of categorization abilities and the processes underlying categorization will make important contributions toward our understanding of how the young child acquires knowledge about his or her world. The aim of the research described in the proposal is to investigate developmental change in two kinds of abstraction capabilities which are central to many theories of categorization. Four experiments are proposed to examine "feature" abstraction in infants ranging in age from 3 to 16 months. Specifically, the experiments attempt to map out important changes across age in the nature of the information infants are capable of using to relate category instances. Two additional experiments are proposed to examine the abstraction of "category-level" information, that is, information that is characteristic of a category as a whole, but not given in any individual instance. The experiments focus on developmental change in memory for category-level information versus memory for idiosyncratic, exemplar information. The experiments employ some variation of either standard habituation or visual preference procedures commonly used in the study of infant perception and memory. The research findings should be of value in adding to our basic knowledge of the development of the normal infant. In addition, because many of the issues under investigation are of interest to the general field of cognitive psychology, the proposed research may contribute to a more general understanding of categorization processes. Finally, the research will serve as a foundation on which to base future investigations of the cognitive functioning of populations of infants at risk for impaired intellectual functioning.